glSeparableFilter2D builds a two-dimensional
separable convolution filter kernel from two arrays of pixels.

The pixel
arrays specified by (width, format, type, row) and (height, format, type,
column) are processed just as if they had been passed to glDrawPixels,
but processing stops after the final expansion to RGBA is completed.

Next,
the R, G, B, and A components of all pixels in both arrays are scaled by
the four separable 2D GL_CONVOLUTION_FILTER_SCALE parameters and biased
by the four separable 2D GL_CONVOLUTION_FILTER_BIAS parameters. (The scale
and bias parameters are set by glConvolutionParameter using the GL_SEPARABLE_2D
target and the names GL_CONVOLUTION_FILTER_SCALE and GL_CONVOLUTION_FILTER_BIAS.
The parameters themselves are vectors of four values that are applied to
red, green, blue, and alpha, in that order.) The R, G, B, and A values are
not clamped to [0,1] at any time during this process.

Each pixel is then
converted to the internal specified by internalformat. This conversion
simply maps the component values of the pixel (R, G, B, and A) to the values
included in the internal (red, green, blue, alpha, luminance, and intensity).
The mapping is as follows:

Internal Format Red Green Blue Alpha Luminance Intensity

GL_LUMINANCE R

GL_LUMINANCE_ALPHA A R

GL_INTENSITY R

GL_RGB R G B

GL_RGBA R G B A

The
red, green, blue, alpha, luminance, and/or intensity components of the
resulting pixels are stored in floating-point rather than integer They form
two one-dimensional filter kernel images. The row image is indexed by coordinate
i starting at zero and increasing from left to right. Each location in the
row image is derived from element i of row. The column image is indexed
by coordinate j starting at zero and increasing from bottom to top. Each
location in the column image is derived from element j of column.

Note that
after a convolution is performed, the resulting color components are also
scaled by their corresponding GL_POST_CONVOLUTION_c_SCALE parameters and
biased by their corresponding GL_POST_CONVOLUTION_c_BIAS parameters (where
c takes on the values RED, GREEN, BLUE, and ALPHA). These parameters are
set by glPixelTransfer.

GL_INVALID_ENUM
is generated if internalformat is not one of the allowable values.

GL_INVALID_VALUE
is generated if width is less than zero or greater than the maximum supported
value. This value may be queried with glGetConvolutionParameter using target
GL_SEPARABLE_2D and name GL_MAX_CONVOLUTION_WIDTH.

GL_INVALID_VALUE is generated
if height is less than zero or greater than the maximum supported value.
This value may be queried with glGetConvolutionParameter using target GL_SEPARABLE_2D
and name GL_MAX_CONVOLUTION_HEIGHT.

GL_INVALID_ENUM is generated if format
is not one of the allowable values.

GL_INVALID_ENUM is generated if type
is not one of the allowable values.

GL_INVALID_OPERATION is generated if
glSeparableFilter2D is executed between the execution of glBegin and the
corresponding execution of glEnd.

GL_INVALID_OPERATION is generated if height
is one of GL_UNSIGNED_BYTE_3_3_2, GL_UNSIGNED_BYTE_2_3_3_REV, GL_UNSIGNED_SHORT_5_6_5,
or GL_UNSIGNED_SHORT_5_6_5_REV and format is not GL_RGB.

GL_INVALID_OPERATION
is generated if height is one of GL_UNSIGNED_SHORT_4_4_4_4, GL_UNSIGNED_SHORT_4_4_4_4_REV,
GL_UNSIGNED_SHORT_5_5_5_1, GL_UNSIGNED_SHORT_1_5_5_5_REV, GL_UNSIGNED_INT_8_8_8_8,
GL_UNSIGNED_INT_8_8_8_8_REV, GL_UNSIGNED_INT_10_10_10_2, or GL_UNSIGNED_INT_2_10_10_10_REV
and format is neither GL_RGBA nor GL_BGRA.